The present invention relates to a walking aid, more particularly to a locking mechanism for use in a frame walker. Frame walking aids has been used to help the disabled or the old with mobility to increase their independence, and it is of great importance to their life. Most of the walking aids are foldable and easy for transportation and storage. However, the structure is rather complex and not easy for the user to operate, and due to its high weight and price, it is to not as widely used as expectation.